This specification relates to image processing.
Moiré patterns are optical effects that can appear in various images and video. For example, moiré patterns can appear in print images (e.g., newspaper print, comic books, etc.) and video content (e.g., television/cable broadcasts and/or streaming video). The moiré pattern can be an undesirable effect that degrades the quality of the images and/or video and/or distracts a user/viewer.
Halftone images (e.g., images that use dots varying in shape, size and/or spacing, to simulate a continuous tone) that are downscaled (e.g., reducing the size of the original image) and/or images with high-contrast alternating color lines are particularly susceptible to the moiré effect. For example, FIG. 1 illustrates a zoomed in portion of a black and white halftone gradient pattern 102. As seen in FIG. 1, the halftone gradient pattern 102 includes dots of various sizes and spacing. When the halftone gradient pattern 102 is viewed from a distance (e.g., zoomed out), the halftone gradient pattern 102 appears as a continuous gradient pattern 104. FIG. 1 also illustrates an example downscaled reproduction 106 of the continuous gradient pattern 104. As seen in FIG. 1, the downscaled reproduction 106 includes the moiré pattern that can be introduced when downscaling the continuous gradient pattern 104.